Immunologic and cellular changes accompanying the therapy of pollen allergy.

We had found previously that children with ragweed hay fever were somewhat less symptomatic after preseasonal immunization with large doses of ragweed pollen extract than were placebo-treated children. To study further the immunologic changes which accompany immunotherapy, these children were treated again the following year. Each patient served as his own control. Serum blocking (IgG) antibody, measured by inhibition of antigen-induced leukocyte histamine release, was increased 20- to 40-fold after therapy. The anticipated postpollen season increase of serum reaginic (IgE) antibody, measured by passive sensitization of leukocytes from nonallergic donors, was suppressed. Instead, the mean titer was decreased after treatment. Total serum IgE levels, measured by radial radioimmunodiffusion assay, were higher than normal; were correlated with reaginic antibody titers; and also did not increase in the pollen season after treatment. The concentration of both IgE and reaginic antibody was lower in the older children, irrespective of treatment. Leukocyte response to ragweed antigen E and guinea pig anti-IgE antiserum was assessed by means of in vitro histamine release techniques. After treatment, the leukocytes of 21 patients were less sensitive (11 cases), or less reactive (10 cases), to antigen E. Response to anti-IgE antibody also was diminished after treatment. In four cases, neither anti-IgE nor antigen E induced histamine release, although both IgE protein and ragweed-specific IgE antibody were present in the patients' own sera. Clinical improvement was correlated best with decreased leukocyte sensitivity and leukocyte reactivity to ragweed antigen E. It appeared that decreased cell sensitivity was related to lower serum reaginic antibody levels. Decreased cell reactivity, in the presence of both IgE protein and IgE antibody in the serum, may indicate a change in cellular response mechanisms. These studies suggest that clinical improvement following specific immunotherapy must be the result of complex changes in the immunologic and cellular components of allergic disease.